Analysis of Tip Leakage Vortex Instability and Blade Force in a Low-Speed Compressor Cascade

Abstract Turbulence model Detached Eddy Simulation (DES) is utilized to conduct detailed research on the tip leakage flow (TLF) instability and its influence on the compressor cascade blade static pressure distribution. The objectives are to investigate the tip leakage flow instability and blade aerodynamic force oscillation at 0deg incidence design state. This research found that the trailing edge leakage vortex and the secondary leakage vortex mixed with the leakage vortex along the backflow direction and involved into the main leakage flow, which is close to the adjacent blade pressure side. The trailing edge broken tip leakage vortex has influenced the adjacent blade pressure side static pressure distribution and vorticity transformation in the tip region. More substantial convective effects are captured in 0.95span compared with 0.7span, based on the vorticity transport equation, which confirmed the tip leakage vortex caused momentum transfer in the tip region occupies a dominant role among the spanwise. The vortex core identification has revealed the tip leakage vortex wandering in the passage. The data-driven decomposition methods proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) helped clarify that the tip leakage vortex has a distinct influence on the adjacent blade pressure side static pressure spatial distribution. The frequency spectrum analysis of blade aerodynamic force indicated that some frequency components are close to the monitored tip region velocity. Then, the DMD characteristic frequency and POD time coefficient frequency corresponding with the mode vortex cohesive structure filled the gap in visualizing the vortex structure with its characteristic frequency, which caused the blade aerodynamic oscillation. Tip leakage vortex instabilities and their influence on the blade are well analyzed. Predicted tip leakage vortex instabilities and the blade force oscillation can utilized in the compressor blade vibration design and flow control.